The invention relates to an apparatus and a process for solids-fluid separation and to products obtained by such a process.
It is known to separate solids from gases by imparting a rotating movement to a solids-gas mixture which is introduced substantially horizontally and tangentially in a vertical cylindrical body (e.g. a cyclone) from which gas is discharged at the top and solids are discharged from the bottom. The discharged gas usually still contains a substantial amount of solids which, to a large extent, can be removed by subsequently introducing the solids-containing gas tangentially into a second-stage cyclone.
However, in order to attain substantially complete removal of small solid particles (e.g. catalyst fines) from gases, as required in e.g. catalytic cracking processes, a third separation stage is usually required. It is known to use cylindrical cyclones with axial entry of a solids-gas mixture for such a purpose.
A disadvantage of three-stage solids-fluid separation is that in many cases the third stage separation means have to be located in a separate housing, particularly when carried out at an elevated temperature and pressure. This requires an additional pressure vessel and transfer lines. Alternatively, when three separation stages are incorporated in a single housing, complex supporting means will be required to cope with temperature expansion problems.
Moreover, the pressure drop over three separation stages will have an adverse effect on the possible recovery of power from fluid discharged at elevated pressure from a third separation stage.